Method of bleaching cotton piece goods



3 150,918 METHOD OF BLEACH ING COTTON PIECE GGGDS Raymond R. Currier,Pittsburgh, Pa, assignor to Pittsburgh Plate Glass Company, Pittsburgh,P3,, a corporation of Pennsylvania No Drawing. il iled Mar. 29, 1962,Ser. No. 183,412 3 Claims. (Cl. 8-111) The present invention relates tothe bleaching of cotton goods. More particularly, the present inventionrelates to the bleaching of cotton piece goods. Still more particularly,the present invention relates to an improvement in the bleaching ofcotton hosiery.

The term cotton goods as used herein in the speci fication and claimsmeans fabric composed entirely of cotton as well as unions or mixturesof cotton fibers with other fibers such as rayon, nylon and othersynthetic and natural fibers easily blended with cotton fibers. Theunions or mixtures above contemplated generally contain at least percentcotton by weight of the cloth. The cotton goods also include clothcomprised of cotton or cotton unions which have been woven and/ orknitted.

In the bleaching of cotton piece goods, such as cotton hosiery, recourseis had to special techniques and equipment to insure adequate treatmentof the goods for a desired degree of brightness. The bleachingtechniques employed by the prior art on piece goods such as hosiery arein general batch type operations as opposed to the continuous bleachingmethods used in treating cloth in open width form. Thus, to achieve adesired degree of bleaching for a specific batch of cotton piece goodsor cotton yarn considerable expense is incurred in chemical costs forbleaching solutions. In addition, the bleaching operations asconventionally carried out require considerable time to achieve thedesired bleaching effect, thereby adding to the overall cost of theoperation.

Thus, for example, in the operation of one of the conventional processesof the prior art, cotton piece goods such as cotton hosiery are scoured,washed, and treated with an aqueous hypochlorite solution in a rotarydyer. After thorough wetting of the goods in the dyer, the bleachsolution is heated in the machine to an elevated temperature to insurefull bleaching action. After a period of time, usually one-half hour,the goods are washed and treated with hydrogen peroxide as an antichlor. This treatment also involves heating of the peroxide solution toan elevated temperature. The goods are then treated with water to Washresidual chemicals therefrom and are then ready for further finishing,such as by treatment with solutions containing optical or fluorcscentwhiteners.

As can be readily seen. processes of the above type require the heatingof treating solutions to elevated temperature and washing steps, both ofwhich are time consuming and costly. A conventional process such asdescribed above requires three hours or more to provide cotton piecegoods such as cotton hosiery in a finished condition. in addition,processes of this type are quite costly from the standpoint of thechemical requirements for a given degree of bleaching on any specifictype of cotton piece goods.

Piece goods, as employed herein in the specification and claims. refersto goods which are comprised essentially of individual units or articlesof cotton cloth which are normally treated in batch type operations.Typical of materials embraced by the term piece goods are socks.stockings and other'forms of hosiery. towels, underwear. shirts.sweaters, blankets, bedspreads and other like cotton material in articleor unit form. Also included are cotton yarns contained on spools.

In accordance with the present invention, there has been States Patent 0provided for the art an improved method of bleaching cotton piece goods,particularly cotton hosiery, which method reduces substantially many ofthe problems formerly encountered in conducting bleaching operations onthese materials. Thus, the time required for a given degree of bleachingon any specific type of cotton piece goods is reduced substantially,usually at least to 200 percent or more. In addition, substantialreductions in chemical costs for a given bleaching operation are readilyattained. By substantially reducing the time required for a givenbleaching operation, plant productivity is increased to a significantextent. Still further, the process requires no specialized equipment andmay be readily adapted to the equipment presently employed to conductbatch bleaching of piece goods in a conventional manner.

Thus, it has been found according to the present invention that inbleaching cotton piece goods, particularly cotton hosiery, excellentbleaching of the material may be readily accomplished by thoroughlysaturating the goods in an aqueous alkaline solution of hydrogenperoxide to provide the goods with a solution content of between 250 and600 percent by weight, basis the weight of the dry goods, and thencontacting the goods with steam at elevated temperatures, usuallybetween 210 and 212 F. for a period of at least fifteen minutes.

Bleaching, in accordance with the teachings contained herein, isconducted in equipment that is conventionally employed to bleach cottonpiece goods such as hosiery. Typical of machines utilized for thispurpose is the Turbo Rotary Dyeing Machine manufactured by the TurboMachine Co. of Lansdale, Pennsylvania, and shown on page 182 of theTechnical Manual of the American Association of Textile Chemists andColorists, volume XXXV. As can be readily seen in the reference referredto, these machines are constructed of an inner perforated basket,usually cylindrical in shape which is contained in an outer solid shell.The inner shell is rotated by a drive means connected to a suitablemotor. The outer shell of the dyer is equipped with an inlet for theintroduction of the bleaching fluids and a suitable outlet is providedfor emptying fluids from the machine.

Spools of yarn are conventionally bleached by treatment in packagedyers. Typical of the package dyers employed for this purpose are theTurbo Package Dyer, manufactured by the Turbo Machine Co. of Lansdale,Pennsylvania, and the Gaston-County Package Dyer manufactured by theGaston-County Dyeing Machine Co. of Stanley, North Carolina. Thesemachines are shown on pages 182 and 177, respectively, of the TechnicalManual of the American Association of Textile Chemists and Colorists.This equipment may be readily employed to conduct the bleachingoperation herein contemplated to provide enhanced bleaching of spools ofcotton yarn.

Bleaching solutions utilized in the instant process are aqueous alkalinesolutions of hydrogen peroxide. The alkalinity of the aqueous peroxidesolutions is usually imparted by alkali metal hydroxides such as sodiumor potassium hydroxide employed therein though alkaline earth metalhydroxides may also be employed. The quantity of alkali metal oralkaline earth metal employed in any given aqueous peroxide solution isconsiderably variable. Conveniently, the alkali metal or alkaline earthetal concentration in the aqueous peroxide solutions is such that a pHof between 8 and 13 is provided in the solution. Preferably, the alkaliconcentration is sufiicient to impart a pH of between 10 and 12 to theaqueous peroxide solutions.

Aqueous alkaline hydrogen peroxide saturating solutions as employedherein conveniently contain less than three (3) percent hydrogenperoxide (anhydrous) by weight of the bleaching solution. Usually thehydrogen peroxide (anhydrous) content of the solution is between 0.1percent to about two (2) percent by weight. Preferably, baths employinghydrogen peroxide (anhydrous) concentrations of between 0.3 to 0.7percent by weight basis the weight of the solution are utilized. Theaqueous alkaline hydrogen peroxide solutions can be utilized during thesaturation phase of the operation at ambient temperatures (70 F.) aswell as at elevated temperatures. A temperature range in these solutionsof between 85 F. to about 110 F. has been found particularly desirableduring the saturation cycle for the bleaching of cotton hosiery.Generally, temperatures which reach or exceed the boiling point of thebleaching solutions are to be avoided.

In addition to the hydrogen peroxide contained in the bleachingsolutions herein employed, small quantities of alkali metal silicatesare usually present therein. The use of an alkali metal silicate in theaqueous alkaline peroxide bleaching solutions has an enhancing effect onthe bleaching solutions. Typical of the silicates contemplated for useherein is sodium silicate having the composition Na O(SiO where x is avalue between 2 and 4. Concentrations of between 0.1 and 3 percent byweight of solution of 42 Baum sodium silicate (Na O(SiO are convenientlyemployed. Preferably an 0.5 percent by weight concentration is employed.

In applying the bleaching solution to the goods to be bleached,considerable care should be maintained to provide adequate saturation ofthe cloth. Thus, the cloth should contain at least 250 percent by weightbleaching solution therein basis the weight of the dry goods and maycontain up to 600 percent solution by weight. Preferably, solutionpick-up is regulated so that a pick-up between 300 and 450 percentsolution by weight is obtained. Solution pick-up of the goods may beconveniently regulated by regulating the volume of bleaching solutionintroduced into the treatment vessel. Thus, if a solution weight pick-upof cloth of 300 percent is desired on a 100 pound batch of cottonhosiery, 300 pounds of bleach solution will be required. As a practicalmatter, an excess of solution over that desired for saturating the drygoods to a given degree is employed since most equipment utilized iscapable of containing small quantities of solution in areas not incontact with goods contained in the equipment. This residual liquidcapacity can be easily determined for any particular piece of equipmenthowever and this quantity of solution is added to the quantity necessaryto give the desired pick-up. Thus, in a rotary dyer of 100 poundcapacity where it was desired to provide a 300 percent solution pick-upor 300 pounds of solution, the volume of bleach solution would becalculated by dividing the 300 pounds of solution desired by the weightof the bleach solution in pounds per gallon. This would provide therequired volume of bleaching solution in gallons. Rotary dyers of 100pound capacity usually hold between 12 to 14 gallons of solution whichdoes not enter the inner cloth containing basket. Thus, to the gallonsof solution required to supply the desired 300 percent pickup, anadditional 12 to 14 gallons of solution are added.

For a more complete understanding of the instant invention, reference ismade to the following examples which are illustrative of methods whichmay be employed in carrying out the novel bleaching process hereindisclosed:

Example I A Turbo Rotary Dyer of 100 pound (dry goods) capacity wasemployed to prepare the bleaching solution. Fifty gallons of water wereintroduced into the machine through a liquid intake and the water washeated by steam coils located in the bottom of the machine to 90 F. Tothe water contained in the machine was added 0.8 pound of flake causticsoda (NaOH), 2.5 pounds of 42 Baum sodium silicate (Na O(SiO and 8.3pounds of 35 percent hydrogen peroxide. The inner basket of the machinewas rotated during the addition of chemicals to assist in the dissolvingof the chemicals. The rotation of the basket was stopped and to theinner basket was added a batch of gray cotton socks weighing pounds. Theinner basket was closed and the outer shell also closed and the basketagain rotated for five minutes to thoroughly saturate the socks. Thisprovided a solution pick-up of 300 percent basis the weight of the drysocks. The excess solution was drained from the machine by opening thedrain valve in the bottom of the shell encompassingthe basket. Leavingthe drain open, live steam was admitted to the machine through a steaminlet at a temperature of 212 F. for a period of twenty minutes. Hotwater F. to F.) was then introduced through the liquid inlet and thebasket again rotated to thoroughly wash the goods. After washing forfive to ten minutes, the rotation of the basket was discontinued, themachine drained, and the socks were bleached to a full white.

Example II Cotton yarn mounted on spools and placed in a package dyersuch as a Gaston-County package dyer previously referred to may bebleached in a similar manner within the purview of the instantinvention. Thus, in treating cotton yarn, the bleaching solution isadmitted to the dyer in quantities suflicient to give the desiredsolution pick-up on the yarn. The solution, after the yarn has beensaturated to the desired degree, is then removed from the dyer and steamis admitted at temperature of usually 210 F. to 212 F. for twentyminutes. After steaming, the yarn is washed with water, preferably hot(160 F. to 180 F.) and the yarn is bleached to a full white.

In utilizing the instant process, recourse to high temperature steamingsteps may be had if the equipment is capable of withstanding thecorresponding pressures. Some package dyeing machines can withstandsufiicient pressure to permit the steaming operation to be conducted attemperatures up to about 240 F. Generally, where high temperaturesteaming is contemplated, temperatures of between 220 F. to 230 F. areemployed.

Usually in the bleaching of white cotton hosiery and other likematerials, optical bleaching agents are employed. These fluorescentbrightening agents are conventionally added to the goods after thebleaching and washing steps have been completed. When they are addeddirectly to the bleaching solutions and heated therein during bleachingas has been the practice in the past, they are found quite frequently tobe rapidly depleted and the absorption on the cloth is often uneven andunsatisfactory. In the applicants process, these fluorescent brightenersmay be added to the bleaching solution with no difficulty and uponcompletion of the steaming operation the goods are found to containadequate quantities of brightener thereon and uniformly distributed.

Example III A three liter volume of aqueous solution is preparedcontaining 4.1 percent H 0 (50 percent), 1.5 percent Na SiO and 0.5percent NaOH by weight of solution. The solution also contains 0.075percent Uvitex V.R. (a water soluble optical bleach manufactured by CibaCo. Inc.). Two cotton socks of 100 percent cotton are immersed in thesolution for twenty seconds and then removed. The wetted socks areplaced in an autoclave and steamed for forty-five minutes at 212 F.,washed and dried. E mple IV bleach contained on the two samples can bedetected.

As can be readily seen from the above examples and description, thepresent process provides considerable reductions in time for bleachingcotton piece goods while still providing adequate bleaching. Inaddition, considerable savings of chemical costs is accomplished sincethe bleaching solutions herein employed can be reused due to the factthat little heat is employed directly on the solutions themselves.

Certain references have been made herein to optical bleaches orfluorescent brightening agents. Typical of the substances embraced bythese terms are the chemicals listed on page 322 of the Technical Manualof the American Association of Textile Chemists and Colorists, volumeXXXV, under the heading Fluorescent Brightening Agents.

While the invention has been described with reference to certainspecific embodiments thereof, it is not intended to be so limited exceptinsofar as appears in the accompanying claims. This application is acontinuationin-part of US. patent application Serial No. 12,265, filedMarch 2, 1960, now abandoned.

I claim:

1. A method of batch bleaching cotton piece goods comprising introducingsaid goods into an aqueous alkaline solution of hydrogen peroxide, saidsolution containing between 0.2 and 3 percent hydrogen peroxide byweight of solution 0.1 and 3 percent sodium silicate by weight ofsolution and having a pH of between 8 and 13, wetting said goods withthe solution until the solution content of the cloth is between 250 to600 percent by weight basis the weight of dry cloth, removing the goodsfrom contact with solution and steaming the wet goods at temperature offrom 200 F. to 240 F. for at least fifteen minutes.

2. A method of batch bleaching cotton piece goods comprising introducingsaid goods into an aqueous solution of hydrogen peroxide, said solutioncontaining between 02 and 3 percent hydrogen peroxide by weight andhaving a pH of between 8 and 13, wetting said goods with solution toprovide between 250 to 600 percent solution in the cloth by weight basisthe weight of the dry goods, separating the wet goods from the solution,and steaming said Wet goods at temperatures between 200 F. to 240 F. forat least fifteen minutes.

3. A method of bleaching cotton piece goods comprising introducing saidgoods into an aqueous alkaline hydrogen peroxide solution containing 0.2to 3 percent hydrogen peroxide by weight, 0.1 to 3 percent sodiumsilicate by weight, and having a pH of 8 to 13, said solution beingmaintained at a temperature of between F. to F., wetting said goods withsolution to provide between 250 to 600 percent solution in the goods byweight basis the weight of the dry goods, separating the wet goods fromthe solution and heating said Wet goods by direct contact With steam attemperature of between 200 F. to 240 F. for at least fifteen minutes.

References Cited in the file of this patent UNITED STATES PATENTS2,029,985 Clark et al. Feb. 4, 1936 2,194,358 Hundt et al Mar. 19, 19402,202,478 Bell May 28, 1940 2,220,682 Kauffmann et al. Nov. 5, 19402,334,066 Campbell et al. Nov. 9, 1943 2,740,689 Easton et al. Apr. 3,1956 2,903,430 Butler Sept. 8, 1959

1. A METHOD OF BATCH BLEACHING COTTOM PIECE GOODS COMPRISING INTRODUCINGSAID GOODS INTO AN AQUEOUS ALKALINE SOLUTION OF HYDROGEN PEROXIDE, SAIDSOLUTION CONTAINING BETWEEN 0.2 AND 3 PERCENT HYDROGEN PEROXIDE BYWEIGHT OF SOLUTION 0.1 AND 3 PERCENT SODIUM SILICATE BY WEIGHT OFSOLUTION AND HAVING A PH OF BETWEEN 8 AND 13, WETTING SAID GOODS WITHTHE SOLUTION UNTIL THE SOLUTION CONTENT OF THE CLOTH IS BETWEEN 250 AND600 PERCENT BY WEIGHT BASIS THE WEIGHT OF DRY CLOTH, REMOVING THE GOODSFROM CONTACT WITH SOLUTION AND STEAMING THE WET GOODS AT TEMPERATURE OFFROM 200*F. TO 240*F. FOR AT LEAST FIFTEEN MINUTES.